1. Field of the Invention
The present invention relates to a printed circuit board (PCB) having a flow preventing dam and a manufacturing method thereof, and more particularly to a PCB having a flow preventing dam, in which the flow preventing dam is provided on the peripheral area of the PCB so as to prevent the outflow of an underfill solution which is introduced between the PCB and a semiconductor chip which is flip chip bonded thereto.
2. Description of the Related Art
With the recent advancement of electronics industries, there is a demand for increasing performance and functionality of electronic components and reducing the size thereof. Accordingly, high integration, slimness and fine circuit patterning are also required on a substrate for surface mounting components, such as SIP (System in Package), 3D package, etc.
In particular, in techniques for mounting electronic components on the surface of a substrate, a wire bonding process or a flip chip bonding process is utilized for electrical connection between an electronic component and a substrate.
The wire bonding process includes bonding an electronic component having design circuits to a PCB using an adhesive, connecting a lead frame of the PCB to a metal terminal (i.e., pad) of the electronic component using a metal wire to transmit and receive information therebetween, and molding the electronic component and the wire with thermosetting resin or thermoplastic resin.
The flip chip bonding process includes forming an external connection terminal (i.e., bump) having a size of tens of μm to hundreds of μm on an electronic component using a material such as gold, solder or another metal, and flipping the electronic component having the bump so that the surface thereof faces the substrate and is thus mounted on the substrate, unlike the mounting operation based on the wire bonding.
Although the wire bonding process has higher productivity compared to other packaging processes, it needs wires for connection to the PCB, and thus the size of a module is increased and an additional procedure is required. Hence, the flip chip bonding process is mainly employed.
FIGS. 1 and 2 are views showing a process of packaging a flip chip semiconductor package according to a conventional technique.
As shown in FIGS. 1 and 2, the flip chip bonding according to the conventional technique is performed in a manner such that solder balls 16 are attached to the connection pads 14 of a PCB 12 and a semiconductor chip 18 is mounted on the PCB 12 by means of the solder balls 16.
In this way, however, when the semiconductor chip 18 is mounted on the PCB 12, a gap G is formed between the semiconductor chip 18 and the PCB 12 due to the height of the solder balls 16 attached to the connection pads 14 of the PCB 12, undesirably weakening the ability to support the semiconductor chip 18 and causing cracks around the soldering portion of the solder balls 16. In particular, in the case where a temperature change occurs, the coefficient of thermal expansion between the semiconductor chip 18 and the PCB 12 is different, and thus thermal stress is applied to the solder balls 16, thereby causing cracks on the solder balls 16.
Hence, with the goal of stably supporting the semiconductor chip 18, an underfill solution 22 of a liquid material is introduced into the gap G between the semiconductor chip 18 and the PCB 12 using a dispenser 20.
The underfill solution 22 is introduced in a small amount between the semiconductor chip 18 and the PCB 12 and thus functions as an adhesive for holding the chip and plays a role in protecting the chip from the external environment, unlike a conventional semiconductor molding material (EMC) for packaging the entire semiconductor chip 18.
However, in the course of introducing the underfill solution 22 using the dispenser 20, part of the underfill solution 22 which is introduced into the gap G between the semiconductor chip 18 and the PCB 12 may undesirably overflow the outer edge of the PCB 12 from the position where the dispenser 20 is located, causing defects.
In order to solve this problem, there have been proposed methods of forming a dam on the peripheral area of the PCB using a dispensing process.
However, the dispensing process which is used to form a linear dam through linear extrusion of epoxy resin from a dispensing nozzle is problematic in that the width of the dam may be non-uniform, and the shape of the dam may become winding due to frictional force at the end of the dispensing nozzle.
Further, an additional dispensing apparatus is required to form the dam, and a process for forming the dam should be additionally carried out.